Apparatus for the generation of order pulses by means of punched cards



06t- 30, 1962 L. KAISER 3,061,189

APPARATUS FOR THE GENERATION OF' ORDER PULSES BY MEANS OF PUNCHED, CARDS Filed July 29, 1959 4 Sheets-Sheet 1 L. KAISER APPARATUS FOR THE GENERATION OF ORDER PULSES Oct. 30, 1962 BY MEANS 0F PUNCHED CARDS Filed July 29. 1959 4 Sheets-SheeiI 2 l i i l 23, l l

7 m25 I 0. 28 5U 292 1 -ssosl AV v 'v Figzu L. KAxsER 3,061,189 APPARATUS FoE TEE GENERATION oF ORDER PULsEs Oct. 30, 1962 BY MEANS OF PUNCI-IED CARDS Filed July 29, 1959 4 Sheets-Shet 3 selon 12| n Tab /fvve'vroa arf/4R KAISER by MS; @64M Oct. 30, 1962 KAISERV 3,061,189

APPARATUS FOR THE GENERATION OF ORDER PULSES BY MEANS OF PUNCHED CARDS Filed July 29, 1.959 4 Sheets-Sheet 4 United States Patent Onlice 3,031,189 Patented @et 30, 1952 3,061,189 APPARATUS FOR THE GENERA'HON 0F ORDER PULSES BY MEANS F PUNCHED CARDS Lothar Kaiser, Reinach, Aargau, Switzerland, assignor to Maschinenfabrik A.G. Menziken, Menziken, Aargau,

Switzerland Filed July 29, 1959, Ser. No. 330,419 Claims priority, application Switzerland Aug. 6, 1.958 17 Claims. (Cl. 23S-61.11)

The invention relates to apparatus for the generation of order pulses by means of punched cards.

Such arrangements may be employed with advantage, for example, for the automatic control of machine tools. The invention has for its airn to provide a particularly simple arrangement of this type which may be used inter alia for the aforesaid purpose.

In the arrangement according to the invention a pulse unit continuously generates electrical pulses which are fed to a counting unit which feeds them to a punched tape, and wherein a processing unit so processes counting pulses received from the counting unit by way of the punched tape that, on arrival of a counting pulse whose ordinal number is equal to a number represented by holes in the punched tape, it emits through the same punched tape in an order unit order pulses which are represented by holes in the punched tape.

An example ot an arrangement according to the invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a diagram illustrating the general principle according to the invention,

FIGURES 2a and 2b are circuit diagrams showing the internal connections of the units illustrated in block form in FIGURE l,

FIGURE 3 illustrates a punched tape, and

FIGURE 4 shows diagrarnmatically a part of a lathe with the arrangement described with reference to FIG- URES l, 2a, 2b and 3 applied to' it.

The illustrated arrangement (FIGURE 1) comprises a pulse unit 1, a counting unit 2, a processing unit 3 and an order or control unit 4 and serves to generate electrical order pulses according to a record carried on a punched tape 5.

The pulse unit 1 (see FIGURE 2a) comprises a perforated disc 6 which is mounted, for example, on a shaft 7 of a copying lathe to be automatically controlled by the arrangement. The perforated disc 6 comprises a ring of holes S which, on rotation of the shaft 7, causes the light emanating from a lamp 9-to impinge intermittently upon a photo-electric cell 10, whereby timing pulses are sequentially generated, which are fed through a line 11 to the counting unit 2. A switch 12 provided in the pulse unit 1 to determine the direction of rotation comprises a ring 13 which is loosely mounted on the shaft 7 and is held in contact therewith `by a spring 14. The ring 13 is provided with a contact arm 15, which is disposed between two ixed contact members 16 and 17 which are connected through lines 18 and 19 to two relays 20 and 21 of the counting unit 2. When the shaft 7 rotates in the direction denoted by the contact arm 15 is turned in the same direction by friction of the ring 13 on the shaft 7Y and comes into contact with the contact member 16.

Consequently, the relay 20 is energised. On rotation of the shaft 7 in the direction denoted by on the other hand, the relay 21 is correspondingly energised.

The relay comprises three normally open contacts 201, 202 and 203, that is to say` contacts which are closed on energisation of the relay. Similarly, the relay 21 cornprises three normally open contacts 211, 212 and 212.

The input line 11 for the counting pulses is connected to a relay 22 which comprises a single normally open contact 221. Connected in series with the contacts 221 and 203 is an electromagnet 23, and in series with the contacts 221 and 213 is an electromagnet 24. The electromagnets 23 and 24 are provided with normally open contacts 231 and 241 and with stepping armatures 25 and 26 which co-operate with a stepping wheel 27 of a rotary switch 28. The rotary switch 2S comprises two brushes 291 and 292 which are staggered at 180 with respect to one another and rigidly connected to the stepping wheel 27 and which are connected to a slip ring 30 and co-operate with ten contact members arranged along an arc of 180, which are connected to ten sensing brushes 31 through ten lines a numbered 1, 2, 3 9, 0. The slip ring 30 is connected to the contacts 231 and 241 through brushes.

The sensing brushes 31 are arranged to scan the perforated tape 5 and to read the records represented by the holes. When a hole in the punched tape .5 is positioned below a brush 31 this brush cornes into Contact with a contact plate 32 situated on the other side of the punched tape 5.

In the illustrated zero position of the brushes 291 and 292, the brush 291 is connected to the line a0, while the brush 292 is connected through an eleventh Contact member to a line 33 which leads to the contacts 202 and 212 and through these contacts to two electromagnets 34 and 35 respectively.

The electromagnets 34 and 35 are in turn provided with normally open contacts 341 and 351, and with stepping armatures 36 and 37 which cto-operate with a stepping wheel 38 of a rotary switch 39, which is designed in the same manner as the rotary switch 28. The rotatable brushes of the rotary switch 39 are denoted by 401 and 402 and the slip ring 41. Ten lines l), which are numbered l, 2, 3 9, 0, lead to brushes 42 arranged on the punched tape 5, opposite which brushes there is situated on the other side of the punched tape a contact plate 43.

The eleventh line 44 extending from the rotary switch 39 leads to the contacts 201 and 211 and through these contacts to two electromagnets 45 and 46. The electromagnets 45 and 46 are in turn provided with stepping armatures 47 and 4S, which co-operate with a stepping wheel 49 of a rotary switch 50. The rotatable brushes of the rotary switch 50 are denoted by 511 and 512 and the slip ring by 52. Ten lines c, numbered 1, 2, 3 9, 0, lead to sensing brushes 53 arranged on the perforated tape 5, opposite which brushes there is situated on the other side of the punched tape a contact plate 54. The slip ring 52 is continuously maintained at positive potential.

In the present example, only three rotary switches 28, 39 and 50 are illustrated for the sake of simplicity, by which switches the units, tens and hundreds of the ordinal numbers of the pulses can be counted, as will hereinafter be more fully explained. However, it will be apparent that further rotary switches could be provided in the same manner to count the thousands, ten-thousands and so on.

The processing unit 3 comprises a signal generating relay 55 having two normally open contacts 551 and 552, which is connected to the Contact plate 54. A second signal generating relay 56 having two normally open contacts 561 and 562 is connected through the contact 552 to the contact plate 43, while a third signal generating relay 57 having a normally open contact S71 is connected through the Contact 562 to the Contact plate 32. The contacts 551, 561 and 571 are connected together in series, the contact 551 being connected to a contact plate 58 situated below the punched tape 5.

On the other side of the punched tape 5, fourteen brushes 59 connected to lines d numbered from 1 to 14 are situated opposite the contact plate 58. Situated within the lines d are fourteen order or control relays R1, R2 R14. All the lines d are connected in parallel with one another and together are connected in series with a slow-acting electromagnet 60 which is provided with a stepping armature 61 co-operating with a stepping wheel 62. The stepping wheel 62 is xedly connected to a feed roller 63 which has at its ends two rings of teeth 64 which engage in feed holes 65 (see FIGURE 3) in the punched tape 5, which extends in the form of an endless band around the feed roller 63 and an idler roller 66.

The brushes 31, 42, 53 and 59 and the Contact plates 32, 43, 54 and 58 combined to form a rod-shaped reading head 67 which extends transversely in relation to the direction of forward movement of the punched tape 5. The punched tape 5 need not by any means have the form of an endless band, but may also be designed as a rigid rectangular card. However, a punched tape having the form of an endless band facilitates the reproduction of the same series of order pulses with the same punched tape, because it can be fed back to its initial position merely by forward stepping of the stepping wheel.

The order relays R1 to R14, when energised, emit through their contacts electrical order or control pulses which may be employed for the most varied purposes.

Before these purposes are explained with reference to an example of an application of the described arrangement, the operation of this arrangement itself will rst be explained.

Each time a hole 8 in the rotating perforated disc 6 frees the path for the light coming from the lamp 9 to the photo-electric cell 10, the relay 22 is energised and its contact 221 is closed. Assuming that the shaft 7 is rotaing in the direction, the relay is energised, as v previously explained, and the contacts 201, 202 and 203 are consequently closed. By closing of the contact 221, the circuit 221, 203, 23, is closed, so that the electromagnet 23 forwardly rotates by one step the stepping armature 26 and consequently the rotary brushes 291 and 292 in the positive direction, while the contact 231 is closed. The brush 291 is connected to the line al, whereby however no circuit is closed. The succeeding counting pulses also only result in a further forward step of the brushes 291 and 292 of the rotary switch 28. Even when the brush 31 of the line a4 touches the Contact plate 32 through a hole in the punched tape 5, nothing happens, because the contact 562 is open.

After a half-revolution of the brushes 291 and 292, the brush 292 is connected to the line 33 and a circuit 231, 30, 292, 33, 202, 34, is closed. As a result of the closing of this circuit, the electromagnet 34 is energised and the stepping wheel 38 of the tens rotary switch 41 is further turned by one step by its stepping armature 36, but this results in no further action. The brushes 401 and 402 are further rotated by one step after each ten counting pulses without anything happening, until nally after 10X10 counting pulses the brush 402 has completed `a half-revolution and is connected to the line 44.

A circuit 341, 41, 402, 44, 201, 45, is thereby closed, so that the electromagnet attracts its stepping armature 48, which moves the hundreds rotary switch forward by one further step. After each hundred counting pulses, the brushes 511 and 512 are moved forward by one step without anything further happening until the brush 511 is connected to the line c3 after three hundred counting pulses, the brush 53 of the said line touching the contact plate 54 through a hole in the punched tape 5. A circuit S11, c3, 54, 55, is then closed, so that the relay 55 is energised and closes its two contacts 551 and 552.

When the tens rotary switch 39 has been moved forward by six further steps after sixty further counting pulses, so that the brush 401 is connected to the line 116, of which the brush 42 touches the contact plate 43 through a hole in the punched tape 5, a circuit 341, 41, 401, h6, 43, 552, 56, is closed. The rel-ay 56 thereby energised closes its two contacts 561 and 562.

When, after four further counting pulses, the brush 291 of the units rotary switch is connected to the line a4, of which the brush touches the contact plate 32 through a hole in the punched tape 5, a circuit 231, 30, 291, a4, 32, 562, 57, is energised. The relay 57 thereby energised closes its contact 571, whereby a signal generating circuit 571, 561, 551, 58, d3//d7//dl0//dl2, 60, is closed. Consequently, the order relays R3, R7, R10 and R12 are energised and emit through their contacts a number of order pulses.

The electromagnet 60 responds with delay, so that the energised order relays have emitted the order pulses before it pulls up its stepping armature, which steps the stepping wheel 62 forward by one tooth. By this forward stepping, the punched tape 5 in the reading head 67 is stepped forward by one line distance.

When the shaft 7 rotates in the direction, the arrangement operates completely analogously, except that, instead of the relay 20, the relay 21 is energised, and consequently the electromagnets 24, 35 and 46 respectively are energised through the contacts 213, 212 and 211 instead of the electromagnets 23, 24 and 45 respectively. The rot-ary switches 28, 39 and 50 respectively therefore rotate in the negative direction, which corresponds to a subtraction of the counting pulses. The counting unit 2 thus operates with plus and minus counting pulses.

For a better understanding of the described arrangement, there will now be explained by Way of example an application thereof to a copying lathe, of which a few essential parts are diagrammatically illustrated in FIG. 4. According to this ligure, the perforated disc 6 and the direction control switch 12 are mounted on the lead screw 7 of the lathe. Mounted on the lead screw 7 in the usual Way is a screw-threaded sleeve 69 xedly connected to the feed slide 68. A copying slide 70` is so mounted on the slide 68 as to be displaceable perpendicularly to the direction of movement of the slide 68. The copying slide 70 supports a cutting tool 71 and its position is determined in known manner by a pattern 72, against which a feeler 73 mounted on the copying slide 70 is pressed, for example hydraulically.

A workpiece 74 which is to be given the illustrated form is clamped on the one hand in a chuck 75 rotating on the working spindle of the lathe and is on the other hand held by a tailstock centre 76. The path which the cutting point of the tool 71 is to describe is indicated in chain lines and is marked by the numbers I VI. A similar path is also described by the point of the feeler 73. The rst six lines of the punched tape S, FIG. 3, are accordingly denoted by I VI.

On the line I, in the case of the hundreds, tens and units, the digit O is indicated in each instance by a hole. In addition, there are holes for emitting energising pulses numbered 2, 8, 9 and 11 for the order relays R2, R8, R9 and R11.

When the line I is brought into the reading head 67, these relays are immediately energised after 0 pulses,

and the order pulses emanating therefrom effect the following operations:

(a) The pulses of the relay R2 engage a variable-speed gearing with clutch which drives the work spindle carrying the chuck 75 at the speed n1.

(b) The order pulses of thek relay R8 start a rapid-feed motor.

(c) The order pulses of the relay R9 set intermediate wheels fo the aforesaid variable-speed gear to forward feed.

(d) The order pulses of the relay R11 set the hydraulic copying lathe to advance.

After emission of these orde-r pulses, the slow-acting electromagnet 60 effects the forward stepping of the punched tape S by one line. At line Il, the reading head 67 reads the number 97. For the sake of simplicity, it will be assumed that the rotation of the shaft 7 between two consecutive pulses corresponds to a forward feed of 1 rnm. of the slide 68, although in reality this feed amounts to 1/100 mm., but the counting unit2has tive rotary switches. The tool 71 consequently moves by 97 mm. in the axial direction up to the point II, at which the orders stored in line II are carried out, while the movement in the direction perpendicular thereto is limited by the pattern 72.

At the point II, the order relays R2, R5, R9 and R11 are energised in accordance with the marking of line II.

The order pulses of R2, R9, and R11 do not vary the existing state. The order pulses of R5 engage a different forward feed speed sl, i.e. a different speed of rotation of the lead screw 7, whereby the rapid movement is discontinued.

After further stepping to line III, the number 240 is read thereon. The point III, at which the orders of line III are carried out, is situated 24() mm. to the left of the point I. At the point III, R2, R6, R9 and R11 are energised. The order pulses of R2, R9 and R11 do not vary the existing state. The order pulses of R6 engage a lower forward speed s2 instead of the forward speed s1 heretofore engaged.

After further stepping to line IV, the order relays R3, R5, R9 and R11 are energised at the point IV with the axial co-ordinate 34() mm., the order relays R9 and R11 producing no change. The order pulses of R3 engage a speed n2 for the working spindle instead of the speed nl, while the order pulses of R5 change the forward feed speed back to s1.

After further stepping to line V, the order relays R1, R8, R and R12 are energised at the point V with the axial co-ordinate 500 mm. The relay R1 ensures that the working spindle remains stationary, the relay R8 ensures rapid forward feed, the relay R10 ensures backward feed and the relay R12 ensures return of the copying slide 70.

In the succeeding, undesignated corner of the path diagram of the tool 71, nothing further happens other than that the return movement of the copying slide 73 ceases when it reaches its outer end position, while the feed slide 68 continues to approach its initial position with rapid movement.

After ve hundred counting pulses, this initial position is reached again at the point VI :1, whereafter in accordance with line VI the order relays R1, R4, R12 and R14 are energised. While nothing else changes, the relay R4 ensures stoppage yof the feed slide 68, and therefore of the spindle 7, and the relay R14 initiates by the pulse emitted thereby, that is to say, the last pulse of the programme or operating cycle produced by the punched tape, the return feed of the punched tape to its initial position.

For this purpose, the relay 14 is slow-acting and comprises normally open contact R141 which on the one hand is connected to the contact plate 58 and on the other hand is at positive potential. When the punched tape 5 has been stepped forward by one further line by the pulse energising the relay R14 and the electromagnet 60, the

contacts 551, S61, S71, thus opening, the contact R141 closes with delay, so that, since a hole is again opposite the brush 59 o-f the line d14 in this next line, a circuit R141, 58, d14, R141, 60, is closed, whereby the relay R14 is again energised and the punched tape is stepped forward by a further line. This cycle continues as long as only the order hole 14 is present in the lines, as shown in FIG. 2.

Of the order relays R1-R14, only the operations of the relays R7 and R13 have not yet been mentioned, because they have not been required in the described operating cycle. The relay R7 may ensure, for example, the engagement of a very slow forward feed (inching feed), while the relay R13 ensures forward stepping of the punched tape 5 when the counting unit 2 is stationary in response to a signal indicating completion of an operation or after a certain time, as will hereinafter be more fully explained.

It will be assumed that, after machining of the workpiece 74, FIG. 4, a thread is to be cut on the forward end thereof. There will then be provided in the line Vl, instead of the order h-ole in `column 14 for the forward feed, the order hole in column 13 for the energisation of the order relay R13, which comprises normally open con- I tact R131, which is connected to an automatic screw .tape 5 could not move further forwards without special further steps.

When the screw-cutting attachment 77 to which Voltage is applied through lines 78 and 79 has automatically cut the desired screwthread, it emits an output pulse to a relay 80 in a circuit -I, 78, 77, 80, 77, 79, The relay 80 has a normally open contact 801, which on the one hand is connected to the electromagnet 60 and on the other hand to positive potential. On energisation of the relay 80, a circuit I, 801, 60, is consequently closed and the lpunched tape 5 is thus moved forward by one line, at which, for example, an order hole 14 for the forward feed is provided, so that the punched tape 5 can be returned to the initial position by successive order holes 14, or further orders can be imparted after a brief further feed.

The energisation of the relay 80 can take place in two ways.

Firstly, when a member of the screw-cutting device establishes that the thread has been cut and the order has thus been carried out, and signals this by closing the circuit of the relay 80'. This is a so-called follow-up control. Secondly, when a particular time has elapsed after energisation of the screw-cutting attachment by the relay contact R131, which time is in all circumstances sufficient for carrying out the order.

Instead of the screw-cutting attachment 77, any other automatic working device could naturally be provided, more especially a device for automatically exchanging a workpiece treated in accordance with the provided oper ating cycle for an untreated workpiece. In this case, the relay R13 is energised when the punched tape 5 has been almost completely returned into the initial position by continuous feed. During the exchange of the workpieces, the punched tape remains stationary. When the exchanging device signals, by energising the relay 80, that the exchange of the workpieces is complete, the punched tape 5 then automatically reestarts and a new operating cycle commences.

In the present example, the movement of the slide 70 is effected by the pattern 72 as usual a copying lathe, but a second arrangement of the described type could be provided to control the movement of this slide 70 in accordance with a given programme by means of a corresponding punched tape. Naturally, the programmes of the two punched tapes employed to control the tool 71 must then be exactly adapted to one another. It is readily possible to employ order pulses emanating from a punched tape to control the other punched tape, for eX- ample to feed it forward. Such an automatic control in two coordinates will be of particular interest for drilling apparatus.

It is also to be noted that the counting holes and the order holes, which lie on one line in FIG. 2, could be located on two lines offset in relation to one another, i.e. the counting holes on a counting pulse line and the order holes on an associated order pulse line. The counting pulse line and the order pulse line Will, however, preferably be aligned to form a single line.

It is particularly desirable that it should be possible, in the punching of the counting holes, to punch them without any conversion (as in accordance with a binary code), for example simply on the basis of a desired coordinate of a point. The latter will be possible by reason of the fact that counting pulses can be added or subtracted owing to the direction control switch 12 and the appropriate construction of the counting unit 2. In this way, not only is time saved in operation, but further rotary switches can be dispensed with in the design of the counting unit 2, without loss of accuracy, as compared with a counting unit processing only plus counting pulses.

It is also to be noted that, instead of order relays R1-R14 or instead of some of these relays electromagnets may be provided which emit, not electrical order pulses, but mechanical order pulses. Naturally, the number of order relays or magnets is in no way limited to fourteen and orders differing considerably from those described can be imparted thereby, depending upon the purpose for which the arrangement is employed.

What I claim is:

1. In an apparatus for generating control pulses, in combination:

(a) a record carrier carrying a plurality of numerical 4records and a plurality of control element records,

said records being spaced fom each other;

(b) first and second sensing means arranged to scan said record carrier for sequentially reading said numerical records and said control records respectively;

(c) a pulse unit for generating a plurality of timing pulses in timed sequence;

(d) counting means operatively connected to said pulse unit for counting said pulses;

(e) signal generating means operatively connected to said rst sensing means and to said counting means for generating a signal when the number of .pulses counted corresponds to a numerical record read by said first sensing means;

(f)` a plurality of control elements corresponding to respective control element records and responsive to signals generated by said signal generating means to emit a control pulse; and

(g) connecting means for operatively connecting said generating means, said second sensing means, and said control elements for selectively transmitting a signal generated by said signal generating means to one of said control elements when a control element record corresponding to said one control element is read by said second sensing means.

2. In an apparatus as set forth in claim 1, said record carrier being a flat member formed with a plurality of perforations, each of said perforations constituting one of said records.

3. In an apparatus as set forth in claim 2, said record carrier being a punched tape.

4. In an apparatus as set forth in claim l, means for moving said carrier relative to said reading means for Ybeing an electrical signal.

7. In an apparatus as set forth in claim l at least one of said control pulses being an electrical control pulse.

8. In an apparatus as set forth in claim 1, said record carrier being a punched tape formed with perforations therein, means for moving said tape relative to said first sensing means in a predetermined direction, a plurality of said perforations jointly constituting a numerical record, and said first sensing means being adapted simultaneously to sense said plurality of perforations for reading said numerical record.

9. In an apparatus as set forth in claim 8, said plurality of perforations being aligned transversely of said predetermined direction.

l0. In an apparatus as set forth in claim 8, each one of said plurality of perforations constituting a decimal digit of said numerical record.

1l. In an apparatus as set forth in claim 1, said record carrier being a punched tape formed with perforations therein, means for moving said tape relative to said sensing means in a predetermined direction, a first group of said perforations jointly constituting a numerical record and being aligned transversely of said direction, said first sensing means being adapted simultaneously to sense said first group of perforations for reading said numerical record, each member of a second group of said perforations constituting one of said control element records, said second sensing means being adapted to simultaneously sense each member of said second group for simultaneous emission of control pulses from the cor-responding control elements, the members of said second group being aligned transversely of said direction.

12. In an apparatus as set forth in claim ll, said first and said second group of perforations being aligned with each other transversely of said direction.

13. In an apparatus as set forth in claim 1, means for moving said carrier relative to said sensing means responsive to said signal for sequential reading of said plurality of records by said sensing means when said second sensing means reads a control element record correspending to one of said control elements.

14. In an apparatus as set forth in claim l, means for moving said carrier relative to said sensing means responsive to said signal from an initial position for sequential reading of said plurality of records by said sensing means when said second sensing means reads a control element record corresponding to one of a group of said control elements, said means for moving said carrier being further responsive to the control pulse emitted by said one control element of said group of control elements for returning said carrier to said initial position thereof.

15. In an apparatus as set forth in claim l, an operating device responsive to one of said control pulses to perform a predetermined operation; signalling means operatively connected to said operating device for generating a signalling pulse responsive to completion of said operation; and means for moving said carrier relative to said r sensing means responsive to said signalling pulse for sequential reading of said plurality of records by said sensing means.

16. In an apparatus as set forth in claim' 1, signalling means responsive to said control pulse for emitting a signalling pulse with a predetermined delay, and means for moving said carrier relative to said sensing means re- -sponsve to said signalling pulse for sequential reading of said plurality of records by said sensing means.

17. In an apparatus as set forth in claim l, said pulse unit including a rotary pulse generating member alter- 9 l@ natively rotatable in one direction and in the opposite sponsive to the direction of rotation sensed by said direction, and a direction detecting means for sensing the direction detection means. direction of rotation of said rotary member, said counting means being operative for counting said pulses alter- References Ced in the me 0f this Patent natively by sequentially adding the number of said pulses 5 UNITED STATES PATENTS to an initial number and by subtracting said number of 2710 934 Senn June 14 1955 pulses from said initial number, and additional connect- 2741732 Cunnilf-,t-lr-II-zzz Apr 10 1956 ing means interposed between said direction detecting 820km Parsonsbet al Ian 14 1958 means and said counting means for switching said count- 10 2,824,694 Boni Feb- 25, 1958 ing means between adding and subtracting operation re- 2,927,258 Tippel Mar` 1, 1960 

